Answer:
ix chemical elements that comprise Group 2 of the periodic table
Explanation:
Calcium, Magnesium, Barium, Beryllium, Strontium, and Radium are alkaline earth metals.
Explanation:
It is given that The Moon's center is 3.9x10⁸ m from Earth's center. The moon 1.5x10⁸ km from the Sun's center. We need to find the ratio of the gravitational forces exerted by Earth and the Sun on the Moon.
The gravitational force is given by :

It means 
So,

r₁ = 3.9x10⁸ km
r₂= 1.5x10⁸ km
So,

Hence, the ratio of the gravitational forces exerted by Earth and the Sun on the Moon is 5:13.
The frequency of the wave is 6800 Hz
<u>Explanation:</u>
Given:
Wave number, n = 20
Speed of light, v = 340 m/s
Frequency, f = ?
we know:
wave number = 

Therefore, the frequency of the wave is 6800 Hz